Turbomachinery such as high performance gas turbine engines have a compressor and turbine which each include one or more annular banks or rows of axially spaced fixed stator vanes which are positioned between rows of rotatable rotor blades. Each rotor blade is formed with a rotor tip and airfoil and a dovetail-shaped base or root which mounts within a mating, axial slot formed between adjacent dovetail posts on the rim of the rotor disk. The connection between the dovetail root of the rotor blade and the axial slot between adjacent dovetail posts on the rotor disk prevents radial and tangential movement of each rotor blade relative to the rotor disk.
In order to prevent axial movement of the rotor blades, i.e., along the longitudinal axis of the rotor disk and engine, one or more blade retainers are mounted adjacent the axial slots in the rotor disks. These blade retainers must be secured to the rotor disks strongly enough to resist the forces exerted on it by the dovetails of the rotor blades, and yet must be easily removable in order to replace the rotor blades.
The most common method of securing blade retainers to the rotor disk is by bolting, using bolts and nuts circumferentially spaced about the rotor disk. Although bolts provide a strong connection between the blade retainer and the disk, their use also presents some problems. For example, removal of bolts and nuts for maintenance purposes is time-consuming and the bolts must be carefully torqued in order to avoid overstress at the connection. Additionally, bolt holes formed in the blade retainer and rotor disk create localized concentrated stress areas which reduce the cyclic life of such parts, which is a particular concern in view of the high temperatures and high speeds at which the rotor disk and rotor blades are operated within high performance gas turbine engines, particularly within high and low pressure turbine sections. Additionally, bolt heads and nuts protruding from the disk increase the disturbance of the airflow or windage across the disk, increasing the temperature of the surrounding air and resulting in decreased engine performance.
In order to avoid the problems associated with a bolted blade retainer arrangement many boltless blade retainers have been introduced. Examples of such boltless blade retainers are shown in U.S. Pat. No. 4,304,523 to Corsmeier, et al., and U.S. Pat. No. 4,890,981 to Corsmeier, et al., both of which are assigned to the same assignee as the present invention, and the disclosures of which are incorporated herein by reference.
Although such boltless blade retainers have successfully eliminated many of the problems associated with bolted retainer assemblies, some problems remain. Particularly, such assemblies include multiple parts requiring a relatively large amount of machining. In addition to the high cost associated with such machining, maintainability requirements for a hot section component such as rotor blades that require periodic inspection and replacement necessitate an improved mounting arrangement that reduces the complexity and number of parts involved in assembly and disassembly. In addition, a design which reduces the weight of the retainer assembly is desirable.